Role of Bronchoscopy in Early Lung Cancer Screening of High Risk Population

Inclusion Criteria: * Patient is over 40 years in age and is a heavy cigarette smoker.(smoking index is over 400) * Patient has been coughing irritably for 2-3 weeks with a failed treatment and without obvious causes. * The nature of cough changes in a patient who has chronic respiratory disease. * Patient has blood-stained sputum persistently or repeatedly without obvious causes. Patient will be included if accorded with any item of above. Exclusion Criteria: * Patient has dysrhythmia or cardiovascular disease that poses a risk during exercise. * Patient has uncontrollable hypertension (SBP \> 180mmHg). * Patient has severe organ dysfunction (shock, severe hepatic and renal dysfunction, massive hemorrhage of upper gastrointestine, diffuse intravascular coagulation(DIC) and massive hemoptysis,etc). * Patient has blood coagulation disorders (PT\>2 times the upper limit of normal(ULN) or Platelet(PLT)\<50000/ul）. * Patient has severe dyspnea. * Patient is allergic to local anesthetic. * Patient is unable to provide informed consent. * Patient is not an appropriate candidate for or is unable to tolerate flexible bronchoscopy procedures. * Patient has any disease or condition that interferes with completion of initial or follow-up assessments of the effectiveness endpoints. * Patient has demonstrated unwillingness or inability to complete screening or baseline data collection procedures. * Patient participated in a study of an investigational drug or device within the past 30 days prior to participation in this study, or is currently participating in another clinical study. * Patient has pulmonary lesions suspected to be cancer from CT images. * Female patient of childbearing potential has a positive result from a pregnancy test.